1. Field of the Invention
The present invention relates, in general, to a magnetoresistive (MR) read/write head and method for making a MR read/write head, and, more particularly, to a giant magnetoresistive (GMR) read/write head having an electron beam cured insulator layer and method for making a (GMR) read/write head.
2. Relevant Background
The desktop personal computer market continues to demand higher capacity and faster performance from hard disk and tape drives. With applications such as file downloading, increased file sizes, advanced operating systems, and multimedia applications, demand for hard disk drive capacity, for example, is doubling every year. This trend has pushed entry level drive capacities to above two gigabyte (GB). Technologies for storing and retrieving data from magnetic media must also be cost effective. Because lower cost per megabyte (MB) is also desired, the prior practice of simply adding more disks and heads to a hard drive is less and less effective.
Disk and tape drive suppliers continue to increase areal densities, or the number of data bits per square inch, to meet the increasing demand for storage at competitive pricing. However, increasing areal density results in smaller recorded patterns on the disk, hence, weaker signals generated by the read head. Read and write head design are key technologies needed to achieve these capacity increases.
To compensate for the weaker signals, read heads are designed to fly only a few microinches from the magnetic medial. Because this distance is already much less than the size of a dust particle, it is unlikely that further improvements can be achieved by moving the heads closer to the media. Moreover, reliability becomes a significant concern as the heads are moved closer to the media.
Hard disk drives with areal densities under 1.0 Gigabits/in.sup.2 typically use inductive heads. Inductive heads offer low cost and mature processing technology suitable for high volume production. To increase the signal strength from an inductive head, designers have increased the number of turns in the read head as the read signal is directly proportional to the number of turns. Some inductive heads use fifty or more turns in the read/write head. However, increasing the number of turns increases the head's inductance. There is a limit to the amount of inductance a head can tolerate to effectively perform data write operations. Since thin-film inductive heads use the same inductive element for both reading and writing, the head cannot be optimized for either operation. Moreover, the increased inductance decreases the frequency at which data can be written to and read from the magnetic media.
Magnetoresistive (MR) head technology is used to provide higher areal density than possible with inductive heads in both disk and tape drives. MR head structures include an MR element as a magnetic field sensor. A coil is formed above the read head and surrounded by a magnetic yoke that defines a write element. The write element is positioned over or adjacent to the MR element in an integrated structure. Although the coil and yoke are magnetically coupled, they are separated by an insulating material to prevent current flow between the coils and the yoke. In the past, this insulating material comprises thermally-cured photoresist.
MR head technology can deliver up to four times the areal density possible with thin-film inductive heads. Separate read and write heads allow each head to be optimized for one particular function (i.e., reading or writing data). With the MR head, the number of wire turns in the write element can be greatly reduced, resulting in a low inductance head enabling high frequency write operations. Using an MR structure as a read element provides high signal output and low noise compared to inductive heads. MR heads are also less sensitive to head misalignment because the read head can be made much smaller than the write head ensuring that the read head will remain over the much wider data path defined by the write head even if the heads are slightly misaligned.
Magnetoresistive devices or heads utilizing giant magnetoresistance (GMR) are of current technological interest to achieve high areal density recording, Magnetic field sensors based on the GMR effect are designed to measure or sense magnetic field strength. GMR sensors have greater output than conventional anisotropic magnetoresistive (AMR) sensors because GMR sensor structure offers higher magnetoresistance ratio as compared to an AMR sensor. Like AMR sensor, GMR sensors directly detect the magnetic field rather than the rate of change in magnetic field (i.e., flux) therefore, they are useful as read heads for sensing data stored on magnetic media. The output of GMR sensors is frequency insensitive and the sensor produces an output even in a constant magnetic field. GMR devices are sensitive to small magnetic fields and because they can be physically small, they promise higher areal density for magnetic storage devices. These factors make a GMR sensor a desirable choice for read heads.
The GMR effect occurs in metallic thin films comprising magnetic layers of a few nanometers thickness separated by equally thin nonmagnetic layers. Large changes in the resistance of GMR films occur when a magnetic field is applied. Unfortunately, even moderate temperatures above about 180 C. cause interdiffusion between the thin film layers. The interdiffusion reduces the GMR sensitivity of resistance to magnetic field strength. Prior MR processing technology requires temperatures above 180 C. for extended periods of time during formation of insulating materials in the write head and so is incompatible with GMR read elements.
U.S. Pat. No. 5,003,178 issued to Livesay on Mar. 26, 1991 describes a large area uniform electron source. One application of the Livesay electron source is photoresist curing. However, the Livesay electron source as disclosed exhibits several limitations that have prevented the use of electron beam resist curing in the production of read/write heads using GMR materials. A need remains for a process and apparatus for forming thin insulating layers that is compatible with MR and GMR read/write head technology.